1. Field of Invention
The present invention relates to a scanner, and more particularly, to a book scanner having two image scanning units for scanning two adjacent pages in documents bound in volume.
2. Related Art
When using a common photocopier or scanner to scan documents bound in volume, e.g., a book, the book has to be turned to the pages to be scanned, and two adjacent pages divided by a bookbinding cord are placed flatly on a scanning table of the photocopier or the scanner, enabling the photocopier or the scanner to scan the two adjacent pages simultaneously. However, such a scanning approach for two adjacent pages in documents bound in volume has two disadvantages. One is that when a book is opened and placed flatly on the scanning table, the area of the bookbinding cord will curve and rise due to the paper thickness, which makes a part of the pages near the bookbinding cord unable to be pressed flatly on the scanning table, resulting in twisted images. The other is that after being scanned by a single image scanning unit at the same time, the two adjacent pages would be regarded as a single image file, so it's difficult to recognize the bookbinding cord automatically and to archive the image files of the two pages separately, leading to inconveniences in subsequent processing and managing of image files.
In order to solve the above problems, a scanner having two scanning tables was provided for scanning two adjacent pages simultaneously, such as ROC Utility Model No. M277207, ROC Patent No. TW531125, and U.S. Pat. No. 5,359,207. The two scanning tables of a scanner in ROC Utility Model No. M277207, ROC Patent No. TW531125, or U.S. Pat. No. 5,359,207 are connected to each other to form an included angle therebetween, such that a crest line is formed at the connection of the two scanning tables. The bookbinding cord of a book is aligned and placed on the crest line, such that two adjacent pages are placed flatly on the two scanning tables respectively. Thus, the problem that the bookbinding area cannot be pressed flatly is solved.
The scanner disclosed in TW531125 has an image scanning unit with an inverse V-shaped cross-sectional area to fit to the two scanning tables. Two image scanning modules are disposed in the image scanning unit, and two adjacent pages in documents bound in volume are scanned through the two scanning tables respectively. However, the inverse V-shaped image scanning unit in Patent No. TW531125 is customized design, and is not compatible with other types of scanners, which causes inconveniences in management of product parts for manufactures. Also, as two image scanning modules are disposed in a single image scanning unit, each image scanning module cannot be adjusted individually according to the corresponding scanning table. If the manufacturing tolerances of the two scanning tables are different, the two scanning tables would cause different depths of field for corresponding image scanning modules. Therefore, images of the two adjacent pages would have different image scanning qualities, and additional image processing is required.
The scanner disclosed in M277207 has a traditional flat type image scanning unit. One image scanning module is disposed in the image scanning unit, and two adjacent pages in documents bound in volume are scanned through the two scanning tables by the image scanning unit. The image scanning unit is not disposed in parallel to both the two scanning tables. The depth of filed at the outer edge of the two adjacent pages is different from that near the connection of the two adjacent pages. Thus, the image of the two adjacent pages would be twisted, and it is difficult to perform the image processing to correct the twisted image, and the image quality cannot be improved.
The scanner disclosed in U.S. Pat. No. 5,359,207 employs 2-dimensional array light detectors attached, either rigidly or rotatably, at a common edge and disposed in a wedge shaped manner. The opposite edges of the arrays are housed in a base portion. These detectors comprise an array of thin film transistors and sensors that function as pixel element detectors. These thin film elements are generally constructed over a translucent substrate, such as glass, to form a two dimensional detecting surface. Two adjacent pages in documents bound in volume, which are prepared to be scanned, are place over the two arrays respectively. Moreover, the base portion additionally supports a backlight assembly and read-out electronics; the backlight provides the necessary illumination of the adjacent pages, such that the detectors of the arrays receive the light reflected by the pages and transform the light to image data. Then, the read-out electronics output the image data stored in the detectors to other processing units that may use such image data. However, the detectors are expensive, and are not widely used in scanners.